Nudi Pixel: Nudibranchs and Sea Slugs Identification with Photographs

Comment from Richard Willan: I am not sure what species this is, but it is definitely not Phyllodesmium longicirrum. The cerata are flattened, their tips are curled and they have small irregular pustules on their posterior face.

Later, other photographer suggested that this is Phyllodesmium macphersonae. And Richard Willan says No; this is definitely not Phyllodesmium macphersonae because the cerata look to be flattened (they are all circular in cross section in P. macphersonae) and certainly are pustulose (they are all completely smooth in P. macphersonae). I cannot see enough detail of the cerata themselves or the oral tentacles to be sure what it is.